The following invention relates generally to a method and apparatus for determining three-dimensional changes in a surface, and more particularly, is directed to a method and apparatus for optically determining three-dimensional changes in facial contours due to swelling and the like. In many instances, it is necessary to measure three-dimensional changes in facial contours. For example, the surgical extraction of impacted wisdom teeth is followed almost invariably by some degree of post-operative swelling of the related soft tissues. Various anti-inflamatory drugs have been utilized for reducing such swelling. In order to assess the anti-inflamatory effects of these drugs, it is necessary 15 to measure the extent that the swelling is reduced over a period of time. However, one of the major difficulties in investigations of facial swelling is that of accurately measuring the swelling. With the measuring techniques utilized to date, pre-operative and post-operative measurements are taken and the results are compared to obtain an indication of the extent of swelling.
Several measurement techniques have been employed to assess swelling following surgery, including stereophotogrammetry and contrast radiography. The stereophotogrammetric technique is disclosed in an article, D. A. Dixon et al., "Minimal Forms of the Cleft Syndrome Demonstrated by Stereophotogrammetric Surveys of the Face", British Dental Journal, Mar. 7, 1972, pgs. 183-189. In addition to the above techniques, clinical analysis, that is, observation of the patient, has also been utilized to determine the extent of swelling. William B. Linnenberg "The Clinical Evaluation of Dexamethasone in Oral Surgery", Oral Surgery, Oral Medicine and Oral Pathology, Vol. 20, No. 1, 1965, pgs. 6-28.
Still further, mechanical techniques for measurement of swelling have been utilized. For example, with one mechanical method, one arm of a pair of callipers is placed in the interdental space between the mandibular first and second molars and the other arm of the callipers is placed in light contact with the external cheek surface. J. H. Sowray, "An Assessment of the Value of Lyophilised Chymotrypsin in the Reduction of Post-Operative Swelling Following the Removal of Impacted Wisdom Teeth", British Dental Journal, Feb. 21, 1961, pgs. 130-133. However, utilization of callipers does not provide an accurate measurement of the extent of swelling since such measurement is taken at a single point on the cheek. A similar mechanical technique is described in the article "An Investigation into Some of the Factors Concerned in the Surgical Removal of the Impacted Lower Wisdom Tooth including a Double-Blind Trial of Chymoral", by Ian W. Cameron, published in the British Journal of Oral Surgery (1980) 18, pgs. 112-124. However, as recognized on page 21 of this article, the device used therein is only capable of measuring the maximum lateral extension of the swelling of the cheek. It is noted that the latter article at page 121 indicates that a volume measurement would be a true measure of post-operative oedema, but further indicates that no such measurement seems possible unless using a very sophisticated stereophotogrammetric technique. Another mechanical technique that has been utilized is described in the article, P. Lokken, "Bilateral Surgical Removal of Impact Lower Third Molar Teeth as a Model for Drug Evaluation: A test for Ibuprofen", Europ. J. Clin. Pharmacol. 8, pgs. 209-216, 1975. The device of this latter article consists of 16 adjustable plastic screws, eight on each side of the face, on bilateral plates, which are fixed on a facial bow attached to an individual bite-block. The plastic screws are adjusted into touching contact with the skin and are adjusted at each sitting and then compared with pre-operative measurements to give an indication of swelling. However, again, with this device, only point measurements are taken.
In an article entitled "Capturing Facial Surface Information", Photogrammetric Engineering and Remote Sensing, Vol. 52, No. 9, Sept., 1986, pps. 1539-1548, by Keefe and Riley, there is disclosed a manner of mapping a facial surface by projecting a laser light onto the surface and using two cameras to obtain a stereo image. The system automatically digitizes the information using an image analyzer and the system's computer base provides a graphic manipulation of the resulting surface data for use in studying the facial surface. However, this method is disadvantageous since it requires a collimated or laser light source and two cameras.
In an article "Moveable Light-Stripe Sensor For Obtaining Three-Dimensional Coordinate Measurements", SPIE, Volume 360, pps. 326-333, by Agin and Highnam, there is disclosed an apparatus for obtaining three-dimensional surface information that may be used to recognize objects and determine their position and orientation. A lightweight camera and a light-stripe projector using an infrared laser diode are mounted in the hand of a robot manipulator. Image-processing routines locate the stripe in the camera image, and homogeneous coordinate transform techniques are then applied to solve for the three-dimensional coordinates of points illuminated by the stripe. However, this method and apparatus is also relatively complex and difficult to use.
Other references which may be relevant to the present invention include the following:
An article entitled "Ultrasonic Pulse-Echo Measurements in Teeth", Arch: Oral Bio, by Barber, Lees and Lobene, Vol. 4, pps. 745-760, 1969, Pergamon Press, printed in Great Britain; an Article entitled "A Photogrammetric Method Of Measuring The Volume Of Facial Swellings", from the Department of Oral Surgery State Dental School, Malmo and the Department of Photogrammetry, Royal Institute of Technology, Stockholm, Sweden, 1953, by Bjorn, Lundqvist and Hjelmstrom; an article entitled "Stereophotogrammetric Measurement of Normal Facial Asymmetry in Children", pps. 536-548, by P. H. Burke; an article entitled "A Photographic Method of Assessing Swelling Following Third Molar Removal", Int. J. Oral Surg. by Gool, Bosch and Boering, Vol. 4, pps. 121-129, 1975; an article entitled "Noncontact Visual Three-Dimensional Ranging Devices", SPIE, Vol. 283, 3-D Machine Perception, pps. 48-53, (1981), an article entitled "The Facial Plethysmograph: A New Instrument To Measure Facial Swelling Volumetrically", J. Oral Maxillofac Surg., Vol. 43, pps. 346-352, 1985, by Milles, Desjardins and Pawel; an article entitled "The Measurement And Use of Registered Reflectance and Range Data in Scene Analysis", Proceedings of the IEEE, Vol. 65 No. 2, February, 1977, pps. 206-220, by Nitzan, Brain and Duda; an article entitled "Generating Models of Solid Objects by Matching 3D Surface Segments", proceedings of the 8th International Joint Conference on Artificial Intelligence, West Germany, Aug. 8-12, 1983, by M. Potmesil; an article entitled "Trypsin in the Treatment of Swellings of the Head and Neck", American Journal of Surgery, Vol. 96, December, 1958, pps. 787-791, Stuteville, et al.; an article entitled "Regular Pattern Projection For Surface Measurement" from Robotics Research, The Second International Symposium, MIT Press 1985, by Sugihara, et als.; an article entitled "Describing Surfaces" from Robotics Research, The Second International Symposium, MIT Press by M. Brady, et al.; and an article entitled "Minimal Forms of the Cleft Syndrome Demonstrated by Stereophotogrammetric Surveys of the Face", Brit. Dent. J., by D.A. Dixon et al., pgs. 183-189, 1972.
In addition, the following U.S. patents generally describe mapping of three-dimensional surfaces or relate similarly thereto as follows:
U.S. Pat. Nos. 3,805,238; 3,884,577; 4,055,833; 4,091,415; 4,109,237; 4,414,546; 4,468,807; 4,573,193; 4,620,318; and 4,641,349. However, these patents generally describe apparatus and methods which attempt to map three-dimensional surfaces absolutely, that is, without any known reference frame. This renders the methods and apparatus relatively complex and cumbersome to use.